Insulating means or cover for metal baths



Patented F eb. 23, 1943 INSULATING MEANS on COVER FOR METAL BATHS Henry H. Smith, Mount Lebanon, -Pa., assignor to The American Steel and Wire Company of New Jersey, a corporation of New Jersey No Drawing. Application March 10, 1941,

' Serial No. 382,669

6 Claims.

This invention relates to a means for insulating molten metal baths, and particularly to an improved cover or blanket for zinc galvanizing, tin,

ing atmosphere which, of course, is understandable in that it reduces the temperature of'the metal baths.

Various types of covers or blankets have been suggested and used to remedy the above mentioned defects, and while some of them have been satisfactory, others in some respects have not been entirely satisfactory. Some of these covers would decompose or volatilize quite rapidly, which necessitated a frequent replacement thereof. Other covers reacted with the bath, or tended to stick to the galvanized metal as it was withdrawn from the bath.

In the present invention, there is provided a cover or blanket in which all of the above named disadvantages have been eliminated.

Accordingly,- it is one of the objects of the present invention to provide an improved means for insulating molten metal baths, consisting of a cover or blanket which does not decompose or volatilize at the temperatures employed in the bath, and at the same time, a cover which properly insulates the top surface of the molten baths with which it is used from the atmosphere, thereby protecting the same from oxidation and the consequent loss of metal, and the loss of heat by by radiation.

It is another object of the invention to provide an improved cover or blanket for molten metal baths which is inexpensive and yet one which is efficient and effective in its use.

It is a further object of this invention to provide an improved cover or blanket for molten metal baths which can be used indefinitely without recourse of the following specification andclaims.

The improved means of my'invention for insulating the surface of molten metal baths comprises slag wool which is relatively light in weight and has a cotton-like appearance and characteristics. Such slag wool is made by treating molten slag, generally obtained during the tapping of a blast furnace, in an atmosphere of steam, that is, the steam under pressure is made to pass through the molten slag thus obtained so as to provide slag wool.

Any slag containing the satisfactory properties may be used and it has been found that a slag of the following composition is satisfactory for placement, and at the same time, a cover which will permit the galvanizing operations to be conducted without the cover deleteriously or adversely affecting the properties of the galvanized material.

Various other objects and advantages of my invention will become more apparent during the use. Such a slag comprises a mixture of approximately 38.08 per cent silica, approximately 12 per cent alumina, approximately 42.23 per cent calcium oxide, and approximately 6.3 per cent magnesium oxide, together with small amounts of iron oxide, manganese oxide, and sulphur, with percentages of all of the ingredients being by weight.

As hereinbefore mentioned, galvanizing involves the use of a molten mass of zinc, and sometimes lead, upon the upper surface of which the present cover may be employed. The top surface of the molten bath is first skimmed free of the oxides and other foreign elements so that the top surface of the molten metal is clean. The slag wool is then applied to the clean top surface of the molten bath so as to provide a blanket of the desired thickness on the top surface thereof. The amount and thickness of the slag wool employed as a cover or blanket on the bath may .vary considerably, but ordinarily a cover of about 4 inches in thickness produces satisfactory results under ordinary circumstances. To those skilled in the art, the limits within which the thickness may vary will be understood, and the desired amount of cover that should be used in order to reduce oxidation of the bath to a satisfactory point can be readily determined. The cover may be disposed over the entire bath, or part of the bath may be covered in some other manner and the present cover disposed only at the outlet end of the bath where the galvanized material is drawn out therefrom.

It will be seen that the slag wool blanket can easily and conveniently be peeled back from the molten metal surface at any point for any desired purpose, such as for changing the length of immersion of a wire in the molten bath during the galvanizing thereof.

As a result of my invention, it will be seen that there is provided a cover which not only prevents access of air to the bath, but also does not require any material attention during the use of the bath. It will be understood that the cover is not destroyed or adversely afiected by the temperature of the bath but remains in its original form with sufficient continuity to form an 7 effective seal. At the same time, the cover or blanket does not adversely affect the character of the bath and does not tend to alloy with the container for the bath, or stick to the surface thereof.

Also by the use of the cover or blanket of my invention a cost savings can be effected, as it reduces the amount of oxides formed on the surface of the molten bath. Furthermore, savings in fuel costs are obtained, since the slag wool acts as an insulator and prevents the loss of heat by radiation, which results in less fuel being necessary to maintain the bath at any desired operating temperature. It will be understood that the slag wool cover or blanket of my invention is not intended to prepare the surface of the material being galvanized for coating in-the bath or in any way to act as a flux, but merely as an insulating means for the top of the molten metal bath.

From the above description of my invention, it will be apparent that many modifications 0f the same may be devised within the scope thereof and all such modifications are contemplated as may fall within the scope of the appended claims.

I claim:

1. In a process of protecting galvanizing baths against oxidation, the step of placing thereon a cover including a layer of slag wool.

2. The method of galvanizing which comprises providing a bath of molten zinc, passing the articles to be galvanized into and through the molten zinc bath, skimming and cleaning the surface of the molten bath so that the same is free from oxides and other elements, and maintaining a blanket on the entire cleaned surface of the molten zinc by disposing a layer of slag wool of substantial thickness on said cleaned surface so as to insulate the molten zinc.

3. The method of insulating and protecting molten metallic baths from oxidation which comprises disposing a layer of slag -wool upon the surface thereof.

4. The method of insulating and protecting molten metallic baths from oxidation which comprises disposing a blanket of slag wool upon the surface thereof consisting of a mixture of silica, alumina, calcium oxide, magnesium oxide and small amounts of iron oxide, manganese oxide. and sulphur.

5. In the process of coating articles by immersing them in a molten metal bath, the step which comprises covering the surface of the bath with a layer of slag wool.

6. In the process of coating articles by immersing themin a molten metal bath, the step which comprises covering the surface of the bath with a layer of slag wool consisting of a mixture of silica, alumina, calcium oxide, magnesium oxide and small amounts of iron oxide, manganese oxide, and sulphur.

HENRY H. SMITH 

